INDOLE ACETIC-ACID AND ITS METABOLISM IN ROOT-NODULES OF A MONOCOTYLEDONOUS TREE ROYSTONEA-REGIA

A monocotyledonous tree, Roystonea regia, was found to bear root nodul es. The root nodules contained a high amount (16.9 mu g/g fresh mass) of indole acetic acid (IAA). A big tryptophan pool (1555.1 mu g/g fres h mass) was found in the root nodules, which might serve as a source o f IAA production, The presence of IAA-metabolizing enzymes IAA oxidase and peroxidase indicated metabolism of IAA in the root nodules. The s ymbiont isolated from the root nodules of R. regia, a Rhizobium sp., p roduced high amount of IAA in culture when supplemented with tryptopha n. The possible role of this IAA production in the monocotyledonous tr ee-Rhizobium symbiosis is discussed.